wmppp: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/wmppp - from package: wmppp.app

You may install the required package with command apt-get install {package}

Error in other languages:
wmppp: bevel nie gevind nie
wmppp: comandă negăsită
wmppp: comando não encontrado
wmppp: commande introuvable
wmppp: command not found
wmppp: käsku ei ole
wmppp: không tìm thấy lệnh
wmppp: komanda nerasta
wmppp: Kommando nicht gefunden.
wmppp: kommandot finns inte
wmppp: komut yok
wmppp: nie znaleziono polecenia
wmppp: níor aimsíodh an t-ordú
wmppp: no se encontró la orden
wmppp: no s'ha trobat l'ordre
wmppp: opdracht niet gevonden
wmppp: parancs nem található
wmppp: perintah tidak ditemukan
wmppp: príkaz nenájdený
wmppp: příkaz nenalezen
wmppp: команда не найдена
wmppp: командата не е открита
wmppp: 命令找不到
wmppp: コマンドが見つかりません